pneumoconiosis coal miners · pneumoconiosis in coal miners by j. c. mcvittie, m.b., ch.b., d.p.h....

6I8 POSTGRADUATE MEDICAL JOURNAL December I949

IRVINE, L. G., SIMSON, F. W., and STRACHAN, A. S. (1930),Proc. Intern. Conf. on Silicosis in Johannesburg, I.L.O. Studiesand Reports, Series F. (Industrial Hygiene), No. I3, p. 259.

JONES, W. R. (I933), ,. of Hyg., 33, 307.KETTLE, E. H. (I932), Y. Path. and Bat., 35, 395.KETTLE, E. H. (I934), Ibid., 38, 20o.KING, E. J. (I945), M.R.C. Special Report Series, No. 250, p. 73.KING, E. J. (I947) Occ. Med., 4, 26.KING, E. J., WRI6HT, B. M., and RAY, S. C. (I949), Paper read

to the Path. Soc., Great Britain, January, 1949.McLAUGHLIN, A. I. G., ROGERS, E., and DUNHAM, K. C.

(I949), Brit. 3Y. Ind. Med., 6, I84.MINERS' PHTHISIS MEDICAL BUREAU OF SOUTH

AFRICA (1946), Report for the Three Years ending Jy 31,I944 (South African Government Printer).

NEW YORK STATE DEPARTMENT OF LABOUR (1949),Monthly Review, 28, No. 4, April.

PERRY, K. M. A. (1948), Proc. Ninth Intern. Cong. of Ind. Med.,London (in the press).

POLICARD, A. (1947), Proc. Conf. of the Institution of MiningEngineers and Institution of Mining and Metalurgy, London,P. 24.

ROGERS, E. (i944), Paper read to the British Tuberculosis Associa-tion.

SHAVER, C. G. (1948), Radiology, 50, 760.SHAVER, C. G., and RIDDELL, A. R. (I947), J. Id. Hyg. and

Tox., 29, 145.VORWALD, A. J., and CARR, J. W. (1938), Amer. J7. Path., 14,49.

PNEUMOCONIOSIS IN COAL MINERSBy J. C. MCVITTIE, M.B., CH.B., D.P.H.

Senior Medical Officer, Pneumoconiosis Medical Panel, Swansea

In his contribution Dr. Meiklejohn has tracedhistorically the recognition of a relationshipbetween disease and dusty occupation, and hasshown that the ancients were aware of the in-dustrial risk and that they, in fact, attributed thedamage in some degree to the dust they inhaled.Until I83I English medical literature had beendestitute of a single treatise on diseases of tradesand professions. In that year Gregory describedthe postmortem findings in a case of pneumo-coniosis 'with black infiltration of the wholelungs' in a Scottish coal miner. Subsequently-there appeared a number of references to pul-monary disease in coal miners, and valuable andcritical surveys of the literature appear in anexcellent paper on ' Coal Miner's Lung' by LyleCummins and Sladden, in the first report (medicalstudies) dealing with chronic pulmonary diseasein South Wales coal miners published by theMedical Research Council in 1942, and in thescholarly and comprehensive study of the diseaseby Fletcher. Although the reference to coal-miners' pneumoconiosis had priority in ourliterature, the later studies were concernedchiefly with miners' phthisis in metalliferousmines and with silicosis in other industries, and-there was considerable delay in bringing workersin the industries within the scope of the Work--men's Compensation Act. In 1907 the Committeeon Compensation for Industrial Diseases recom-mended that the question of scheduling silicosis(fibrosis due to the inhalation of free silica) shouldbe kept in abeyance for the time being. Later,owing to -successful measures adopted in the goldmining industry in South Africa under successiveMiners' Phthisis Acts, pressurE was brought tobear on the Home Office to deal with the subject.Pressure was brought not only by medical men

but by workers and their representatives who wereconcerned about the incidence of the disease, andwho were alert to the fact that increasing sicknessand disability were associated with changing con-ditions underground. In I925 Grenfell presentedthe evidence he had collected in South Wales. Inone year 22 cases (including 12 deaths) in drillersand ' hardheaders' had been collected from fivecollieries. It was emphasized that in one par-ticular pit the disabled men, whose ages rangedfrom 22 to 45 years, worked in the same place orheading. Four of the group had died and post-mortem evidence was available. In the follow-ing year Tattersall reported the tragic story of agroup of rock drillers in another area. As a resultof these and other representations a method wasdevised of dealing with the difficulties of thesituation in this country by a system of ' schemes 'each applicable to a particular industry or groupof industries. Thus the Various Industries(Silicosis) Scheme, 1928, applied to all workmenemployed at any time on or after January i, 1929,in ' the drilling and blasting in silica rock in orincidental to the mining or quarrying of otherminerals,' and by it silica rock was defined ascontaining not less than 50 per cent. free silica.This scheme identified the disease with particularoccupations and with particular working places,and the drillers, brushers and hardheaders wererequired to prove the analysis of rock. Therewas, too, a strange inconsistency between theabove scheme and the Refractories Industries(Silicosis) Scheme which came into force in I9I9.The latter embraced compensation for partialincapacity as well as death and total incapacity.Certification under the 1928 scheme was by acertifying surgeon who was not required to makean X-ray examination. These anomalies were

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quickly remedied, and since I93I certification ofcoal miners under the Silicosis and Pneumo-coniosis Schemes has been by medical boards whodirect an X-ray examination in every case in-vestigated. This paper is based on the writer'sexperience as a member of the former MedicalBoard for Silicosis and later as a member of aPneumoconiosis Medical Panel of the Ministry ofNational Insurance in South Wales, and on ex-perience in the South Wales coalfields (193I-33),in Lancashire, Northumberland, Durham andScotland (I933-43) and again in South Wales(I943-49), and deals mainly with clinical aspects.Within a very short time it was obvious that on

the medical side silicosis in South Wales minerspresented certain' common features, namely grosslesions of the lungs associaed with varying degreesof disability. The cases were unusual in that theydid not conform to one's experience of the diseaseas seen in other industries because of (a) the ex-treme youth of the patient, (b) the comparativelyshort exposure in underground work, (c) the grossnature of the lesion radiographically and the in-frequency of classical-' snowstorm' opacities inthe lung and (d) the abnormally high incidence incertain mines. There were more applications andcases certified in the anthracite valleys, but theywere not confined to that area. The writer col-lected and analysed all the cases seen in I931-32and found that the age incidence and exposure inthe attributable risk was the same in the anthracite,steam and bituminous areas. Silicosis was adisease of the young driller or ' hardheader ' andof the middle-aged collier. Moreover the diseasewas found in workers not actually engaged incutting, e.g. hauliers, etc. There appeared to besome other factor at work in that, even in highincidence mines, certain colliers worked with im-punity throughout their working lives. Opentuberculosis was infrequently a complication ofthe massive type of lesion. The pathologicalfindings suggested that the. fibroid lesions werecomparable, if not indistinguishable, from the in-fective silicosis described by the South Africanworkers.

Experience in Lancashire and the Scottish coal-fields confirmed these general features of coalminers' silicosis. Although the numbers weresmall, several pits seemed to cause more diseasethan all the other pits in the area. By the end of1933 the number of cases certified in some of theprincipal coalfields was as follows: South Walesand South Western, 500; Staffordshire, I7;North Wales, 2; Scotland, 5; Lancashire andCheshire, 7; Northumberland, i; and Durham,nil. The mine owners were by now contendingthat the disease was not silicosis but pneumo-coniosis, and at a meeting of the medical board

in 1934, Keating reported that he had collected aseries of 59 cases (in South Wales) in which theboard had diagnosed the disease and issued theappropriate certificates. These cases later camebefore the Courts which ruled that the claimantswere not within the scheme, and so their claimsfor compensation were rejected. The records andskiagrams in this series were afterwards examinedby Professor Haldane, who accepted as silicosisthose where work on hardheadings was recordedand classed as pneumoconiosis those withoutrecord of such work. The most notorious high-inicidence mine contained only one seam of silicarock which at its thickest part was only i in. thick.No drifting or heading work had been done in itfor years. There was no mechanical drilling andthe miners did their own ripping in top and bottomshale. The lung disease found in the miners inthis and similar mines was attributed by Haldaneto bronchitis and bronchiectasis, while Jonessuggested that it was due to inhalation of sericite,a hydrous silicate of aluminium and potassium.On looking at the problem as a whole, it seemedimpossible from the medical point of view to drawany practical distinction between silicosis andpneumoconiosis for clinically, radiographically andpathologically they were identical.An amending scheme which extended the pro-

visions of the 1931 scheme to coal miners em-ployed in any occupation underground was intro-duced in 1934.

In 1935 Thomas, who the previous year hadbriefly referred to a type of case frequently en-countered amongst claimants in South Wales,enlarged on the topic from his additional ex-perience in the interval. Many cases were en-countered in the South Wales coalfield where thediagnosis was difficult for the following reasons.The industrial history and clinical findings led tothe conclusion that a pathological process had de-veloped which closely resembled silicotic fibrosis.Many of the men so affected were totally disabled.,The skiagrams in most instances showed anabnormal condition of the lungs which, however,did . not conform to the appearances generallyaccepted as including silicotic fibrosis. The filmscould be divided into three groups showing (a)emphysema only, (b) reticular fibrosis of a coarsetype more or less evenly distributed, and (c)reticular fibrosis of a fine type more marked in themid-zones. Similar cases had been noticed in theManchester area, but it was not surprising whenthe Medical Research Council undertook an in-vestigation of the whole problem in South Wales.After extensive investigations and a monumentalreport by D'Arcy Hart and Aslett, the Committeeon Industrial Pulmonary Diseases accepted theview that dust was the fundamental cause of the


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620 POSTGRADUATE MEDICAL JOURNAL December I949abnormality, but as the relative parts played bythe different components of dust had not beenelucidated they were of the opinion that a non-specific term should be used to describe it. Theytherefore recommended the use of the compre-hensive term ' pneumoconiosis of coal workers,'and also recommended for purposes of compensa-tion that the X-ray standard required for thediagnosis of pneumoconiosis of coal miners shouldinclude reticulation. Following this recommenda-tion the Coal Mining Industry (Pneumoconiosis)Compensation Scheme came into force on July.i,1943. It extended the application of the schemeto classes of workers not previously covered andempowered the medical boards to issue certiflcatesin respect of a wider range of lung conditionscaused by dust. It was always anticipated that theintroduction of the new scheme and the wideningof the definition which made it clear that one ofthe earliest stages of the disease came within thescope of the scheme would result in an increasingnumber of applications and certificates. Thus in1943 the board in West Wales examined 677miners and certified 328. In 1945 they examined3,470 and certified I,828. Certification carriedwith it suspension from the industry, and the lossto coal mines through pneumoconiosis has beenappalling. Between I93I and 1943 seven menwere leaving the South Wales pits every weeksuffering from silicosis, between 1943 and June,I948, 50 men were leaving every week sufferingfrom pneumoconiosis. The pool of pneumo-coniotic ex-miners increased. These figures andthis visible evidence etch in sharp and clear linesthe coal problem -and its associated medicalproblem. They have had other effects. Theyproduced a real dust phobia in the mining com-munities; they tended to cause dissatisfied minersto rationalize all their superficial objections intofear of pneumoconiosis, and they have acted as amighty deterrent to the sons of miners and otherswho might have entered the industry. It may beclaimed that the figures igiven reflect the tragiclegacy of mining conditions and the methods ofmining over the last 30 years, but the marked in-crease in discovered cases in recent years certainlydoes not indicate a worsening in conditions.Between 1923 and 1940 the mines became deeper,drier and dustier. These were the years ofmechanization. In the majority of mines con-veyors were introduced from 1923 onwards.Pneumatic drills had been in use from about I913,but coal-cutting machines were not introduceduntil about 1927 and screening plants in 1934. Allthese intensified the processes and speeded up theevolution of the lesions in the lung. Beforemechanization two colliers working the long-wallsystem would advance about three yards a week

cutting and boxing coal, packing, stowing andripping, doing productive and ' dead ' work. Withconveyors, 10 to 20 colliers work a face shovellingcoal on to the conveyors, doing productive workpractically the Whole time. In these conditionsthe air carries a heavier dust burden from theactivities of a group of men. Occupational riskhere is intensified by the overall industrial risk.But these years were also the years of the X-rayand its increasing use in the diagnosis of pul-monary disease. Already by 1932 many of theapplications on behalf of coal miners in WestWales were supported by X-ray reports. Largelyfollowing the pioneer work of Harper in Amman-ford, some of the Miners' Lodges initiated a systemof periodic X-ray examinations' by private radi-ologists who, by '943, were X-raying 4?000 to5,000 miners each year. Many others were beingX-rayed by tuberculosis physicians. After theintroduction of the I943 scheme with its widerdefinition of pneumoconiosis there was a flood ofapplications to the medical boards, and in I944the South Wales Miners' Federation directed thatevery claim should be supported by a radiologist'sreport. Thus was made general for South Walesthe practice which had been adopted in thewestern districts for many years. The filteringof applications withheld a large number of claims,but it revealed evidence of pneumoconiosis inthousands of others. In his first GoulstonianLecture, Fletcher discussed the increase in cer-tification rates after 1943 and considered the maincauses to be (a) the acceptance of the radiologicalcondition of reticulation, (b) the operation of theEssential Works Order, and (c) moie generalawareness of the disease and intensive rhechaniza-tion introduced into the East Glamorgan pits.However, as the increase in cases certified as dueto silicosis alone in 1943 was 75 per cept. higher,and in 1945 was 300 per cent. higher than theI942 figure, the admission of reticulation ac-counted for slightly less than half the increase. Itis therefore reasonable to suggest that a strikingincrease would have been reported without thenew scheme, and that the alarming figures inSouth Wales arose mainly from what in fact be-came a mass radiographical investigation. Ex-perience has proved that the evidence of the diseasein any industry is proportionate to the number ofX-ray examinations made of the chests of workersexposed to dusts as suggested by Rubin in regardto silicosis.The figures in Tables i and 2 underline some of

the points discussed in the preceding paragraphs.Incidence ofPneumoconiosisThe incidence of the disease is firstly in colliers,

then in firemen and shotsmen, repairers, hauliers,


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December 1949 McVITTIE: Pneumoconiosis in Coal Miners 6zi

TABLE

PNEUMOCONIOSIS AND SILICOSIS IN THE COAL MINING INDUSTRY

Number of new cases certified by the Silicosis Medical Board in Great Britain during the years 1939 to June 30, 1948(1948 figures are provisional)

I Up toRegion 1939 1940 1941 1942 1943 1944 1945 I 946 1947 June 30

1948

Scotland .. .. .. .. 7 2 3 6 I0 I09 148 i66 22 175Northern.. .. .. .. 2 5 2 4 I2 79 57 7INorth-Eastern .. .. .. 6 7 8 6 25 85 95 127 155 8iNorth-Midland .I - I- I ° 1 3 25 17 10North-Western .. .. .. 0 oj0 8 7 27 53 8i 97 136 62Wales .. .. .. .. 418 j 448 499 763 1,155 i,6o8 5,224 3,804 2,867 1,069Midland .. .. .. 12 H 13 24 48 95 132 99 110 64Kent .. .. .. .. '0o 2 1 0 25 30° 71 1 79 59

Total .. .. . 465 484 535 821 1,306 2,o69 ,82I 4,440 3,779 1,584* Pneumocoiiiosis SclieTne.

'FAB[,E 2

PNEUJMOCONIOSIS IN COAI MINES

Cases Certiflie by Silicosis Medical Boards

-1(38 1939 1940 1941 1942 1943 1944 1945 1946Anthracite .. .. .. .. .. .. 205 204 260 261 325 336 792 1,569 620Other South Wales Coal Fields 1.. .. .. 77 183 1i6 213 410 780 813 3,505 3,040

FIG. I.-J.W., aged 52 years; repairer 8 years; hardground borer 7 years; rider 22 years; total 37years. Ceased work because of sudden onset ofdvspnoea. Pneumoconiosis Category 2 withspontaneous pneumothorax (R).

-~~~ ~ ~ ~ .:e ....: ::..@

FIG. 2.-D.R. aged 51 years; repairer 7 years, collier9 years labourer 20 years; total 36 years.Pneumoconiosis Category 3A,


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622 POSTGRADUATE MEDICAL JOURNAL December 1949

Fic. 3.-T.G., aged 38 years; collier 2i years. SimplePneumoconiosis, Category 3.

hard ground men, surface screen workers andunderground labourers in this order. It requiresfor its development on the average I5 to 20 years'exposure. Whereas 25 years ago the incidenceappeared to be chiefly in borers and ' hard-headers,' in West Wales in the period I943-1949only an occasional case was seen where ' hard-heading' was the attributable risk. This wouldappear to justify the claim of the owners that dustconditions in the hardheadings were as good asanywhere underground. An interesting factemerges from an investigation of the incidence inhauliers. Thus the disease is fairly common inhauliers with exposures of 25 to 40 years in con-ditions prevailing between I900-25, but it israrely, if ever, seen in hauliers with similar ex-posures in recent improved conditions. This re-flects a reduction in air-borne dust in the mainroadways. The incidence of disease in colliers intwo collieries, X and Y, with nearly equal popula-tion at risk has been investigated. These col-lieries were chosen because in both go per cent.of all the workers had been X-rayed by privateradiologists. All those with definite X-rayabnormalities, with doubtful skiagrams and even

FIG. 4.-Same case, showing progression after i Imonths.

a few with negative skiagrams made applicationsto the medical board. It can be taken that therest were completely negative. For the purposesof the investigation all those in which the diseasecould not be wholly attributed to the particularcolliery were excluded. The incidence and stageof disease in age groups are shown and the rankingof the collieries as regards dust conditions isindicated.The stages of the disease are based on Gough's

classification in which he divided the pneumo-coniosis of South Wales coal workers into twomain types (a) simple pneumoconiosis and (b)infective pneumoconiosis. The term complicatedpneumoconiosis is preferred here in order notto pre-judge the issue as to the exact causationof the condition-whether due to infection or totoxic action of siliceous dusts. (For details of thecategories in each stage see' X-ray Examination.')

It will be seen from Table 3 that colliery Y hasproduced more disease than colliery X and, what ismore important, it produces it in much earlier agegroups. Thus it has produced pneumoconiosis inI9 colliers under 30 years of age while colliery Xhas produced only three in that age group.


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December I949 McVITTIE: Pneumoconiosis in Coal Miners 623

TABLE 3

Simple ComplicatedPneumoconiosis Pneumoconiosis

Categorou o 2 3 4 A B C D

-_____ - - ------ - ___ __ -. . -___- --- --Age GroupX x Y X YlXjY X Y X Y X Y X Y X Y25-30 .. 2 3 0 3 I 8 o 5 0 0 0 0 0 0o0 0o0 031-40 . . 15 0 7 o i6 13 i I6 o o I 0 0 4 0 0 0 041-50 .. 5 0 I I 0 6 2 6 6 o I I 2 1 I 0 0 0 051-60 3 0 4 0 5 2 3 3 0 00 0 0 I 0 0 0 06i-7o o0 0 I 0 0 O I 0 0 2 0 0 ' 0 0 0

Colliery X: Average depth, 1,500 ft. Very dry. Satisfactory as regards dust concentration.Colliery Y: Average depth. 850 ft. Very dry. Unsatisfactory as regards dust concentration.

The figures in the table seem to confirm theopinion of Jenkins (1948) that the incidence ofsimple pneumoconiosis so far as collieries are con-cerned, can be looked upon as a function of time-concentration of dust. If the incidence ofdisease in the under 30 age group is an index ofdust conditions it is gratifying to report a markedimprovement. Between I943 and 1946 II5 caseswere seen, but between I 946 and I 949 only 3cases in the under 30 age group were found tohave developed pneumoconiosis.

'The duties of the Pneumoconiosis Medical

FIG. 5.-E.G., aged4 years; collier i6 years. Cor-plicated Pneumocorniosis, Category, 3D. Seen ioyears previously the category of the X-ray abnor-malities was 3A.

Panels under the National Insurance (IndustrialInjuries) Act include those that obtained underthe Silicosis and Pneumoconiosis Schemes. Theyare mainly (i) diagnosis of the disease, and (2)assessment of disability. Now advisory functionsare added; moreover assessment has to bedetermined on a percentage basis.

DiagnosisThe diagnosis of the disease rests upon the tripod

cited by Keating in 1930-industrial history,clinical examination and X-ray examination.

1- ,i Fga-2 :....... .... 2

FIG. 6.-P.J. aged 57 years; repairer 23 years, co1lieri9 years; total 42 years. Tuberculosis per se.


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Industrial HistoryMeiklejohn (I949) has contributed a valuable

paper on the importance of the care necessary ineliciting all the facts and he has emphasized thatan expert knowledge of industrial processes is anecessary qualification of the pneumoconiosis ex-pert. A visit to a working place underground isworth more than hours of questions and explana-tions in the examination room. In coal mining,as in other industries, the physician must think ofoccupational risk and of general industrial risk, ofdust created in particular places and of general air-borne dust. He should ask about intensity ofexposure, about length of exposure and shouldenquire how far mechanization has proceeded.The attributable risk may have been in a job whichthe man considered not very important, especiallyif he had left it many years ago. The industrialhistory correctly ascertained is a matter of fact.In the presence of the specific X-ray signs of thedisease it is the most valuable aid in establishingthe diagnosis. In the presence of ambiguousshadows or other X-ray abnormalities, caution isnecessary before basing a diagnosis on the mostsuggestive industrial history.

Clinical ExaminationThere is a tendency to regard clinical examina-

tion in pneumoconiosis as comparatively un-important. This is largely due to the fact that thedisease, like some other miliary nodular diseases,can only be diagnosed by radiological examination.In the writer's opinion, however, thoroughness isof paramount importance and a searching clinicalexamination is necessary for evaluation of thesymptoms, for acquiring expert knowledge of thechest necessary in reading chest skiagrams, fordifferential diagnosis and for the assessment ofdisability. The methods of inspection, percussionand auscultation are by no means discredited.

SymptomsAt the outset it has to be stated emphatically

that symptomatology is often unreliable and varieswith the circumstances and outlook of the patient.Psychologically the attitude of the patient as aclaimant is often quite different from those ob-served in other circumstances, and an objectiveappreciation is necessary. The first and thecommonest symptom is ' tightness of the chest,'a term used by the majority to indicate slightbreathlessness, and by the minority to indicate afeeling of constriction or difficulty in taking a deepbreath. The tightness is often worse in the morn-ing and in close, damp weather. ' Shortness ofbreath,' however, is often an understatement formoderate or even marked breathlessness. Thoughthe onset of these symptoms as stated by the

....... ............................

,K,t...°.,.IM..

:.....~~ .......: ..

FtG. 7.-T.F., aged 34 years; colliery i9 years. Caseof Hodgkin's disease confirmed at post-mortem6 months later.

patient may be unreliable, the breathlessness israrely of recent origin. The patients themselvestend to grade the dyspnoea by the restrictions itimposes; some are ' all right on the level but badon inclines,') some are worse on inclines, ' whileothers have difficulty i-n remaining at work. Ex-cept in a minority of cases these symptoms arecompatible with regular employment and evenwith overtime. A history of a change of occupa-tion from a heavy job to a light job-from a well-paid to a less well-paid-because of chest trouble,is stronger presumptive evidence of the presenceof dyspnoea, and is often more valuable than arecital of symptoms.Cough is second in frequency but it is rarely

the chief symptom. It is usually a short cough,occurring at night and on rising in the morning;and it is not affected by weather changes. In theearly stages of the disease the cough is not relatedto effort but with more advanced disease it is in-duced by exertion. When cough is the chiefsymptom, tuberculosis, bronchitis or emphysemashould be suspected.The majority of the patients complain of a

slight viscid sputum usually black or grey incolour and very few fail to supply a specimenwhen a sputum examination is directed. With theonset of infection the charaecter and quality of the


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sputum changes, but even in the presence ofcharacteristic chest signs and X-ray abnormalitiesit is very difficult to demonstrate tubercle bacilliin the sputum of coal miners. Of great significanceis the sudden appearances of copious black sputumto which the Pneumoconiosis Research Unit havegiven the name ' melanoptysis.' It denotes thebreaking down of a large fibrotic mass in the lungand has prognostic significance.

Pain is probably third in order of frequency andthe most frequent site is behind the sternum. Inmost cases there are no physical signs to explain it.There seems to be no relationship to cough andit is often present without cough. Cardiac diseaseas the cause of pain must, of course, be excluded.Pleuritic pains are fairly frequent and, in a diseaseassociated with superficial emphysematous bullae,spontaneous pneumothorax as a cause of suddensevere pain must not be overlooked. Pain in thelumbar regions is a frequent complaint and thismay be due to irritation of the diaphragm.

Haemoptysis is rare and occurs with com-plicating tuberculosis, mitral stenosis or carcinomaof the lung. ' Stained ' sputum is often mentionedbut its significance is doubtful. Sputum examina-tions in patients presenting this symptom havefailed to demonstrate tubercle bacilli in a singlecase where physical signs in the chest were not alsopresent.Weakness is a very common complaint but is

difficult to relate definitely to pneumoconiosis.Colliers' work is heavy and for years they haveworked under conditions of strain; weakness maybe due to other causes. Deterioration is slow,however, and marked alteration in the severity ofthe symptom is suggestive of tuberculosis or otherserious disease.Once the symptoms of pneumoconiosis are

established they persist. There is no markedperiodicity and seasonal exacerbation as in chronicbronchitis and, except in the rare occurrence ofspontaneous pneumothorax, no sudden changes inseverity occur as in tuberculosis and cancer of thelung.

SignsThe appearance of the patient may give no clue

to the presence or severity of the disease. Theaverage pneumoconiotic collier is fairly stockywith good muscular development. In the absenceof extraneous disease obvious loss of weightsuggests tuberculosis or gross emphysema. Uni-lateral contraction and tracheal deviation alsosuggest tuberculosis. Cyanosis is rare and is seenonly in cases of gross emphysema or cardio-pulmonary disease. Marked pallor may be ob-served where infection has supervened and itspresence calls for a careful examination of the

abdomen and of the haemopoietic and lymphaticsystems. Finger clubbing is not seen in simplepneumoconiosis of coal miners, but in complicatedpneumoconiosis it occurs in cases with bilateralbasal confluent opacities and with open tubercu-losis.When dyspnoea is demonstrable it is invariably

associated with some loss of the mechanicalbellows action of the chest. The average collier,with or without pneumoconiosis, does not use hischest well and it is therefore difficult to detect thefirst signs of departure from the normal. This isseen in more rapid shallow breathing with limiteddiaphragmatic movement. With more markeddyspnoea and increasing fixation of the chest, themovements of the diaphragm become vigorous.The respiratory rate is not always increased, foran asthmatic type of breathing with prolonged andlaboured expiratory phase is associated withmassive fibrosis, as these cases seem to have a gooddeal of spasm. In pneumoconiosis with extensivebullous or focal emphysema the extreme phase isreached; there is marked rigidity of the chestwhich is held in the position of inspiration, withcontraction of sternomastoid, pectoral, intercostaland abdominal muscles, and laboured breathing.Tuberculosis should be suspected in those caseswith considerable dyspnoea not associated withmarked rigidity, and unequal movements shouldsuggest pleurisy, pneumonia or tuberculosis.Until the onset of cardiac failure in the advancedstages of the disease the dyspnoea of pneumo-coniosis always subsides on rest. In the terminalphase the signs and symptoms do not differ fromthose of classical right heart failure.

PercussionIn the early stages there is no change to per-

cussion. Later there may be impairment of thenote over the upper and mid-zones. Differentialimpairment of percussion in the upper part of onelung is suggestive of tuberculosis. Very frequentlyeven when the upper and mid-zones show im-pairment, the note in the axillae and over the lowerlobes is hyper-resonant due to underlying em-physema, and in such cases cardiac dullness maybe diminished.

AuscultationAuscultatory signs are often present before per-

cussion signs. The cardinal sign is a modified,rather high-pitched respiratory murmur bestheard in the right lung in the axillary area. Overthe apices and upper parts of the lungs the murmurmay be normal. In the majority of moderately-advanced and severe cases the breath sounds arediminished at the bases and a feature of the caseshowing massive fibrosis is the presence of silent


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areas over the upper lobes posteriorly. Signs ofbronchitis and bronchiolitis are fairly frequent incomplicated pneumoconiosis but not in simplepneumoconiosis. Sibilant rhonchi are heard in theaxillae and at the bases, and superficial crepitationsat the periphery of the lungs. The presence oftuberculosis will introduce the innumerablephysical signs by which it betrays itself. Althoughdense pleural adhesions are so frequent at post-mortem examinations pleural friction is rarelyheard in life. Except in the advanced stages of thedisease there are no cardiac changes detectable, anduntil those stages are reached the electrocardio-gram shows no change. In what has been calledthe ' cardiac phase,' however, the cardiac soundsare weak and the E.C.G. shows right-sidedpreponderance.

X-ray ExaminationDiseases of the lung cause either increased or

decreased aeration reflected radiographically byincreased or decreased translucence. Increasedtranslucence is found chiefly in the emphysematousstates. Decreased aeration is caused mainly byfluid, secretions and by diffuse and nodularfibrosis. The resulting loss of translucency is re-flected in terms used by chest physicians and byradiologists, ' snowstorm,' 'snowball,' ' sausagemass,' ' pseudo tumorale,' 'cotton wool,' 'pinpoint,' ' pin head,' etc. Professor Gough, whosework has conspicuously clarified our ideas on thesubject, deals with the nature and pathology of thedisease in his contribution. It is sufficient here torecall that the retention of particles of dust in thelungs when intake exceeds output, when the dustfails to reach its physiological destination and iseffectively retained in the lungs, results in smallcollections of dust, i.e. coal nodules. It may beexpected, therefore, that certain properties of thedust, namely, particle size, dosage, toxicity andradio opacity will influence the X-ray picture. Itis doubtful, however, whether particle size doesmore than determine admission to lung alveoli andliability to phagocytosis in the alveoli. It has beensuggested that difference in particle size resulted incoal particles and silica particles reaching separatedestinations in the lung, so producing differentX-ray pictures, but Enid Rogers has shown thatthe earliest coal nodule and the earliest silicoticnodule appear in the same site, i.e. in the lymphtissue at the junction of the respiratory bronchioleand alveolar duct. The effects of dosage are notdifficult to understand. The capacity of certainalveolar cells to remove dust is one of the chiefmechanisms for cleansing the lungs, but when theload is too heavy for the phagocytic ' ride' themechanism breaks down and dust is trapped inthe lungs, it may be in only one or two lobules or,

with more massive doses, in lobules throughoutthe lung. The effect of toxicity of dust particlesis not completely understood and it is too big asubject to elaborate here. But it is possible toexplain the differences in the histology and path-ology of the coal nodule and silicotic nodule (whichdevelops in the same site) by mechanical effects ofmasses of coal dust in the one and by the slowfibrogenic action of dissolved silica in the other.Coal dust is said not to be radio opaque butGough, James and Wentworth have shown thatthere is a very close correlation between the X-rayopacities of simple pneumoconiosis and the coalnodules (with their minimum of reticular fibres).The coal nodules are really collections of coal dust.Some standard of what constitute a disease isdemanded, otherwise legislation may becomepunitive and workers told unnecessarily andwrongly that they have the disease. Such astandard must have some relationship to theaccumulated knowledge and experience of patho-logical changes with special reference to inceptionand development. The reading of X-ray films mayappear to be a routine process, but it requires longexperience in reading normal films, knowledge ofoccupations and risks, personal knowledge of theindividual patient and experience of pathology.Doctors know by what fine shades the normalpasses into the abnormal and in this regard the'normal' chest admits of some departure fromthe normal. It can be stated that in the majorityof cases of simple pneumoconiosis the X-rayappearances reflect the actual dust in the lungs; ina few they show certain associated changes, i.e.emphysema in addition. In complicated pneumo-coniosis the X-ray appearances reflect the dust andfibrotic reaction to the dust and/or tuberculosis.

It is not surprising that there have been manyattempts to draw up a radiological classification forpneumoconiosis. Some were unsatisfactory be-cause they sought to combine stage of disease withdisability and some because they did not describewhat was seen in the X-ray. In I947 Davies andMann published their suggested classification ofthe basic lesions, stages, categories and X-raytypes in South Wales. There is no doubt thattheir classification is the best available and shouldbe studied by those interested. The authorsappreciated that pneumoconiosis varies in itsradiological manifestations from country to countryand from industry to industry and that the diseasefound in South Wales needed its own classifica-tion. Their classification is capable of widerapplication for radiologically coal miners' pneumo-coniosis is the same disease in South Wales,Scotland, Durham, Lancashire and, the Midlands.There may be a geographical variation in therelative incidence of simple and complicated


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December 1949 McVITTIE: Pneumoconiosis in Coal Miners 627

TABLE 4

Simple Pneumoconiosis Complicated Pneumoconiosis

Category o . . Normal A. Localized ambiguous shadowsCategory i . . Minimal B. Massive shadowsCategory 2 . . Moderate C. Advanced massive shadowsCategory 3 . . Marked D. Advanced massive shadows with distortion of thor-acic structures and emphysema

pneumoconiosis, as indeed there is in different pitsin the same county, but examination of skiagramsfrom all the coalfields justifies their hope that theprinciple and broad outline of their classificationwill be applied to pneumoconiosis elsewhere.Gordon Smith is of the opinion that it is the samedisease as is encountered in the New South Walescoal mines.The Davies and Mann classification emphasizes

that the basic radiological abnormalities in SouthWales coal miners are minute opacities, 0.5 toI.5 mm. in diameter (the term micro-nodularused by the French writers is very descriptive butit is better to keep to two-dimensional words). Itabandons the general use of the term reticulation,it provides an instant picture in the mind's eye ofthe anatomic character of the parenchymal disease,it suggests the presence or absence of infection, itindicates distortion of thoracic contents, and itdoes not attempt to relate disability to any categorynor does it define disease. The essentials of theclassification are as follows:-In simple pneumo-coniosis there are four categories of increasingabnormality, the distinction of categories beingmade chiefly on profusion of the opacities, theinvolvement of the periphery of the lung field andthe degree of obscuration of the lung markings.In complicated pneumoconiosis there are alsofour categories, the distinction here being made intype or quality of the opacity. Thus the categoriesare as in Table 4.

In simple pneumoconiosis larger opacities, 1.5to 5 mm., of varying density and outline are alsoseen, and many of the pictures are of mixed types.

Several aspects call for further consideration.In simple pneumoconiosis screening of hundredsof cases has shown that the lungs are generallymobile, in contrast to lungs with complicatedpneumoconiosis where diaphragmatic excursionespecially, is limited. Enlargement of mediastinalglands is not a feature of simple pneumoconiosis.The granular opacities are usually bilateral but areoften more profuse in the right lung, especially inthe middle zone. They are rarely seen above theclavicle. Certain factors, however, may determinethe concentration of the granules. In several caseswith a history of left-sided pneumonia the con-centration of granules has been in the left lung,while an active bronchitis of the right lung pre-

vents the normal selective concentration on thatside. These observations suggest that the featuresof these two pictures are due to decreased or in-creased phagocytosis. In category 3 especially,areas of close aggregation of the nodules is fre-quently seen in the middle longitudinal third ofthe lung, suggesting sometimes a ghost-like outlineof a massive shadow.

Studies of progression have been very limitedbecause under the former Compensation Schemesthe majority of certified miners were not seenagain. However over 500 colliers who returned towork underground after being found to havesimple pneumoconiosis but no disability, havebeen re-X-rayed at intervals during the last sixyears. Davies and Mann state that progression inthis stage of pneumoconiosis is by increase in thenumber of the opacities, but in the period men-tioned above it has been practically impossible todemonstrate a single case of progression by in-crease in numbers. Progression in this way istherefore slow, and the writer questions whethermore than a small minority pass through all thecategories, o to 4, and suggests that it is possiblethat category 3 may follow immediately oncategory o or category i through a sudden break-down in the dust cleansing mechanism of thelung. Progression is fairly frequently recognized,however, in simple pneumoconiosis by the appear-ance, often in the outer third of the upper zone ofthe right lung, of larger opacities, 5 to 7 mm. indiameter, but this heralds the new stage of com-plicated pneumoconiosis. Progression may beseen in the X-ray by a decrease in the opacitiesowing to focal emphysema becoming confluent.Emphysema in simple pneumoconiosis is sug-gested by increased translucency of the inner halfof the lung field, low position of the diaphragm,flattened ribs and especially in one type of skia-gram which reveals a fine reticular network like acobweb with fairly sparse, evenly distributedgranular opacities. This is the only type of film toshow reticulation and the patient is usually over40 years of age. The only cardiac charige worthyof note is a prominent pulmonary conus seen fairlyfrequently in cases where clinically there is grossemphysema. Occasionally due to rotation of theorgan, concentric enlargement appears in theskiagram as an enlarged left ventricle.


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6z8 POSTGRADUATE MEDICAL JOURNAL December 1949

Complicated PneumoconiosisAs already mentioned diaphragmatic excursion

is often limited. Mediastinal glands are enlargedand fibrotic. Of the various opacities found incomplicated pneumoconiosis, first in order offrequency is the single ambiguous shadow in theright upper zone just below the clavicle. Its edgesmay be blurred or sharply defined, and it rarelyexhibits the linear drainage markings of oldinfection. Second in frequency are homogeneousshadows of varying shape, tangerine or reniform,and occasionally triangular. They may appearsingly or in both lungs, and frequently two, threeor even four appear in the sam'e lung. They showa predilection for certain sites. Thus the com-monest site is the right upper zone below theclavicle, the next in order of frequency is the mid-zones of the lungs above and below the inter-lobarsepta. They are often found adjacent to the hilarstructures and in the lower lobes and occasionallythey show circumferential calcification. These,the ' pseudo tumorale' forms of the Frenchwriters, have been carefully studied by Balgairiesand his colleagues who, with Leclercq, found bytomography. that the commonest sites were in the'superior axillary ' and' middle dorsal.' segmentsof the lung. Another frequent picture is that of anumber of irregular, sometimes fluffy shadows inthe middle longitudinal third of the lung. Therehave been better opportunities to study theevolution and progression of these opacities, forthe schemes under which the majority of minerswith this stage of pneumoconiosis were certifiedhave been in force for many years. They areassociated with increasing disability and the menhave returned for re-examination. Although theseopacities are usually superimposed upon simplepneumoconiosis categories 2 and 3, they arefound also in categories o and i. They arise byat least two different processes. In discussingprogression in simple pneumoconiosis, the appear-ance of clusters of larger opacities in the upperzone was described as the development of com-plicated pneumoconiosis. Such opacities may in-crease in numbers down to the mid-zone and tothe base on the same side and to the mid-zonecontralaterally, and they may then become closelyaggregated and later confluent in the sub-apicalregion and mid-zones. Or the opacities mayappear suddenly, often after illness such as broncho-pneumonia and influenza, and in the site of anold fibrotic lesion. Continuing progression isassociated with contraction and increasing opacityof the shadows, peaking of the diaphragm, and thedisappearance of small opacities from the lowermid-zones. The latter is explained by the develop-ment of compensatory bullous emphysema, re-flected in the X-ray by large translucent areas sub-

divided by crescentic lines and shadows whichoccasionally give a 'soap bubble' effect. Theonset of open tuberculosis will modify the appear-ance of the opacities and this will be discussed inthe next paragraph. Radiological progressionunder dust exposure after certification and sus-pension from the industry has been carefullyinvestigated by the Pneumoconiosis ResearchUnit. Fletcher found that the results of theirradiological surveys strongly suggested' that thedevelopment of complicated pneumoconiosis isdue to some factor other than the addition offurther dust to the lungs.The cardiac shadow may become narrower as

the disease progresses, with or without the onsetof open tuberculosis.

Differential DiagnosisIt will be seen that the abnormal shadows found

in pneumoconiosis resemble certain main forms oftuberculosis of the chest. Thus the opacities ofsimple pneumoconiosis resemble those of thenodular form of tuberculosis due to haemato-genous spread of tubercle bacilli. -This may occurwithout a fatal outcome. In miliary tuberculosisthe patient is usually very ill. In healed miliarydisease some of the opacities are calcified, theglands are enlarged and the Mantoux test wouldhelp to establish the diagnosis. Sarcoid diseasemay also closely resemble simple pneumoconiosis,but examination of the skin and bones-especiallythe hands-would confirm the diagnosis.

In low-grade broncho-pulmonary tuberculosisthe commonest site of the lesion is in the apex ofthe lung. The patient may be symptomless, andin the presence of an industrial history diagnosismay be in doubt. Opacities above the clavicleand in the inner third of the upper zone, in thesterno-clavicular angle, especially if they are uni-lateral, veiling of the pleura, radiating fibrousbands and signs of cavitation all suggest tubercu-losis. In fibro-caseous tuberculosis where con-glomerate and irregular dense opacities and streaksare the feature, and where spread is to the base onthe same siae and to the mid-zone of the oppositeside, the picture may closelv resemble moderatelyadvanced pneumoconiosis. The presence ofcavities in the X-ray, sputum and clinical examina-tions help to establish the diagnosis.

In certain other conditions, namely in coccidi-oidomycosis and other fungus infections, in miliaryand lymphatic metastatic carcinoma, in leukaemicconditions, and haemo-siderosis found in mitraldisease of the heart, the X-ray picture closely re-sembles that of simple pneumoconiosis. Theopacities in complicated pneumoconiosis may besimulated by carcinoma, Hodgkin's disease, hyda-tid cyst, thickened pleura or bronchiectasis. Thus


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a complete clinical examination is necessary, withspecial attention to haemopoietic and glandularsystems viith dermal tests if necessary and withskiagrams in oblique and lateral positions.

DisablementThe present Act like the former Compensation

Schemes refers not to accident or disease but topersonal injury by accident or disease; thus, underthe provision of Section I2 of the National In-surance (Industrial Injuries) Act, I946, an insuredperson is entitled to disablement benefit if, as theresult of the relevant personal injury, he suffersloss of physical or mental faculty which is sub-stantial and likely to be permanent. Whatever lossof faculty the claimant sustains he will suffer' somedisability ' from which the normal person of thesame age and sex will be free. The term ' dis-ablement ' is used to denote the aggregate of thedisabilities which arise in a particular case-thatis the aggregate loss of health, strength and thepower to enjoy life. In simple pneumoconiosis itis the emphysema, focal and bullous, which resultsin unequal ventilation with insufficient oxygenationof blood. Massive fibrosis also results in in-sufficient oxygenation of the blood by reduction ofthe capillary bed. The anoxia results in a dis-ability-dyspnoea, defined by Meakins as ' theconsciousness of the necessity of increased respira-tory effort,' and a disability recognizable by theobserver. Definition of disablement in pneumo-coniosis or at least its physical component is easy,but the assessment of disability remains a formid-able problem. To the writer it presented itself inthis way. In the early years, 1930 to I943, inSouth Wales and later in Lancashire, Durham andScotland, claimants appearing before the medicalboard were obviously dyspnoeic, either at rest orafter slight exercise. The loss of faculty wasdemonstrable and required no postulating, butclinical examination was necessary to determinewhether the dyspnoea was respiratory, cardiac orboth. After I943, in the great rush of applicantsto the board, the majority of claimants exhibited noobjective evidence of disablement, though someof them were found to have well-establishedpneumoconiosis. There was the other side of thepicture. When examining claimants the followingtype of case was frequently met--a youngishman, usually under 40 years of age, complainingof dyspnoea on exertion, often borne out by theoccurrence of dyspnoea and sometimes vertigoafter a short exercise tolerance test, rapid pulse(over 8o at rest), and obvious nervous demeanour.To the non-medical mind, such a man was not fitto do heavy work. If the skiagram of this chestshowed simple pneumoconiosis, he would beassessed and suspended from the industry; on

the other hand, if his skiagram was negative hisclaim would be refused, and he would return towork. The point to be stressed is that there wasseldom any difference clinically between thepositive and negative cases. One suspects thatmany of these cases exhibited the classical effortsyndrome and that the finding of X-ray abnor-malities was coincidental. The X-ray is of verylittle value in the assessment of the individual case.Although we have learned by experience that thepathological extent of disease in massive fibrosis isoften in advance of the X-ray signs, the skiagramdoes give a picture of the anatomical extent of thedisease. But it is the functional capacity of theremaining healthy lung or partly damaged lungwhich allows a man to enjoy life and to make hisrespiratory adjustments albeit at the expense ofrespiratory reserve. When the reserve is spent,even slight progression in the disease will result ininexorably increasing dyspnoea.The effects of emphysema in producing a

respiratory ' dead' space with unequal respirationhave been noted, and there is no doubt that emphy-sema which, in some forms at least cannot beestimated by the X-ray, causes more dyspnoea thaneven large areas of fibrosis. It is obvious, too,that there is a mechanical ventilatory componentof pulmonary insufficiency. Observation ofthousands of cases has shown that in the dyspnoeaof pneumoconiosis, ventilatory insufficiency playsa conspicuous part, and this is another reason whyit is impossible to correlate disablement with theX-ray picture. The effects of pleural adhesionsand of fixation of the chest cannot be estimated bythe X-ray. But the X-ray has a ' group ' or' average ' value, and in that way may be an aid inassessment. McCann, Hurtado, Kaltreider andFray applied physiological tests to a series of pul-monary fibrosis cases divided into groups accord-ing to the anatomical type of fibrosis revealed.They concluded that the average value of thechanges were proportional to the degree of fibrosis.Camazian (fils) investigated medico-legal decisions(percentage awards) in 706 pneumoconiotic minersin the Cevennes and came to the conclusion that,in general, functional capacity was in proportionto the X-ray lesions. Experience in South Walesconfirms these general observations but the in-dividual variations in each group and the peculiardifficulty of diagnosing focal emphysema must bestressed.The approach to assessment of disability then

is made on the recognition of certain principles.i. A complete clinical and X-ray examination

and, if necessary, a second or third examination.The close association of certain ' chest ' symptomswith cardiac and cardio-vascular diseases mustconstantly be borne in mind.


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630 POSTGRADUATE MEDICAL JOURNAL December x949

2. The effects of emphysema, focal and bullous,must be included in the disease.

3. Dyspnoea is recognized and demonstrated,and assessment in the individual case is mainly onclinical judgment, aided by exercise tolerance testsor other physiological tests:-

(a) The exercise tolerance test is standardized.(b) The response to the test depends upon many

factors, bronchial spasm, pleural adhesions,' fixed' chest, and the assessment is not furtherloaded by the presence of these conditions.

(c) The dyspnoea demonstrated is divided intoseveral grades with a percentage value for eachgrade.

4. Ideally the X-ray should not be used inassessment, but in the absence of an ideal orpractical physiological test, the assessment is in-creased by adding percentages according to thedegree of fibrosis.(Members of the Penumoconiosis Medical

Panels are at present measuring vital capacity,maximum breathing capacity and minute volumeon exercise by means of apparatus kindly suppliedby Dr. J. G. Gilson and Dr. P. Hugh-Jones,Pneumoconiosis Research Unit, who advised onthe standardization of the exercise tolerancetest.)

In the period 1943 to 1949, 20 per cent. of allapplicants found to have pneumoconiosis had nodisablement. This percentage is made up chieflyof coal miners with simple pneumoconiosiscategories 2 and 3, for in these stages at least36 per cent. have no disablement. When dis-ability is found it is due to the presence of focalemphysema or infection. A few cases with com-plicated pneumoconiosis are found to have no dis-ability, but the majority have varying degrees ofdisablement, again depending on the extent ofemphysema, fibrosis and the presence of tubercu-losis. Thus these two conditions, emphysema and

tuberculosis, dominate all our studies of thedisease.

Deaths from PneumoconiosisIn Great Britain during the eight years I940

to 1947, there were an average of 530 deaths eachyear from pneumoconiosis. Coal miners accountedfor more than half the annual figure. In a valuablestudy of pneumoconiosis in South Wales anthra-cite mines, Gooding made an analysis of 592deaths among certified silicotics. He found that5I6 in the series were due to silicosis and 76 toextraneous causes. Of the ' silicotic ' deaths 145,or 28.I per cent., were due to silicosis accompaniedby tuberculosis. The writer has similarly in-vestigated 300 deaths where full details were avail-able and has divided them into two groups accord-ing to the stage of the disease. The great majorityof deaths from pneumoconiosis and pneumo-coniosis accompanied by tuberculosis are fromcongestive right heart failure, and tuberculosis isgiven as the cause only when haemoptysis occurredor when severe toxaemia and wasting were present.When tuberculosis was present, however, it wasrecorded (see Table 5).

In this series I83 deaths were due to the diseaseand I17 to extraneous causes. In the first group' pneumoconiotic' deaths accounted for 22 percent. and in the second group 76 per cent. of thetotal. Simple pneumoconiosis is not a killingdisease like complicated pneumoconiosis. Analysisof the deaths from compl¶cated pneumoconiosisshows two chief sub-groups, those diagnosed withcategory B and C in the 30 to 40 age group andthose diagnosed in the 6o to 70 age group. In thefirst the average period between certification anddeath is five years, in the second it is six years.As it may be assumed that many of those in thelatter group must have developed complicatedpneumoconiosis at a much earlier age, it follows

TABLE g

Simple ComplicatedPneumo- Pneumo-coniosis coniosis

Pneumoconiosis (C.H.F.) . 6 98Pneumoconiosis Accompanied by Tuberculosis (C.H.F.).. 2 6oTuberculosis 4Spontaneous Pneumothorax 2Pneumonia IO 7Sclerotic, Hypertensive and Degenerative Heart Disease I8 14Valvular Disease of the Heart 2 2Bronchial Carcinoma .. I 3Cancer (Other Organs) 13 6Uraemia 5 4Weil's Disease 2Miscellaneous Causes.. .. .. .. .. .. .. .. .. .. 18 12

Total . .. . .. . .. . .. . .. 86 214


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December I949 WYERS: Asbestosis 631

nevertheless that a considerable number of menwho develop complicated pneumoconiosis whenaged 30 to 40 are a very bad risk. Tuberculosiswas present in 36 per cent. of all pneumoconioticdeaths, in i6 per cent. of all deaths due to simplepneumoconiosis, and in 39 per cent. of all deathsdue to complicated pneumoconiosis. The figure(36 per cent.) of the extent of complicating tuber-culosis in coal miners' pneumoconiosis is higher

than the figure given by Gooding and others,but it is considerably lower than the figure forother industries, especially for slate mining inNorth Wales where tuberculosis is present in 75per cent. of pneumoconiotic deaths.

Finally, one is impressed by the apparently in-creased susceptibility of coal miners with simplepneumoconiosis to pneumonia and acute respira-tory infection.

BIBLIOGRAPHY

BALGAIRIES, E., DECLERCQ, G., JARY, J., and NADIRAS, P.( 948), Revue Medicale Miniere, 2, 12.

CUMMINS, S. LYLE, and SLADDEN, A. F. (1930), J. of Path.and Bact., 33.

CAMAZIAN (FILS), PIERRE (1947), 'Recherches Sur LesPneumokonioses Dans Les Charbonnages.'

DAVIES, I., and MANN, K. (1948), 'Proceedings of the NinthInternational Congress on Industrial Medicine.' (In thepress.)

FLETCHER, C. M. (I948), Brit. Med. J., I, 1015, 1005.GOODING, C. G. (I946), Lancet, 2, 89I.SMITH, GORDON, Personal communication.GOUGH, J., JAMES, W. R. L., and WENTWORTH, J. E.

(1949), 'A Comparison of the Radiological and PathologicalChanges in Coai Workers' Pneumoconiosis,' 3'ournal of theFacuilty of Radiologists, I, I.

GREGORY, J. C. (I83I), Fdin. Med. and Surg. Journal, 36, 389.GRENFELL, D. R., Personal communication.

HART, P. D'ARCY, and ASLETT, E. A. (I942), Special ReportSeries, M.R.C. No. 243 (B).

JENKINS, T. H. (1948), 'Medico-Mining Aspects of Pneumo-coniosis in South Wales.' Paper read before the South WalesInstitute of Engineers.

KEATING, N., Personal communication.LECLERCQ, J., BALGAIRIES, E., BONTE, G., and

DECLERCQ, G. (1948), Revue Medicale Miniere, 4, 23.McCANN, HURTADO, KALTREIDER and FRAY (I937),

journ. Clin. Invest., I6, 23.NIEIKLEJOHN, A. (I949), Lancet, 2, 360, 'Contribution of the

Employment History to Clinical Diagnosis.'ROGERS, ENID (1944), Paper read before the Tuberculosis

Association.RUBIN, ELI H. (1947), 'Diseases of the Chest,' W. B. Saunders

and Co.TATTERSALL, N. (1926), j. of Indus. Hygiene, 8, 466.'I'HOMAS, R. W., Personal communication.

ASBESTOSISBy H. WYERS, M.A., M.D., D.I.H.

Although certain difficulties remain to be ex-plained, the theory that silica is a causative agentin pulmonary fibrosis is widely accepted. When,however, the fibrogenic potentialities of silicatesare considered, these difficulties are very greatlyincreased. Olivine, for example, has been shownto provoke only a foreign body reaction and hasbeen suggested for foundry work, whereasasbestos is notorious. Studievs in mineralogicalcomposition of atmospheric dusts and ashed lungtissue are progressing and to the data foundtheories of solubility and crystal form are beingapplied. If the solubility is high, as in the case ofsilicic acid gels and sols, the material is eliminatedtoo fast to produce fibrosis. A low solubility, suchas in mixtures of quartz and aluminium, equallyretards fibrosis (King, I938). There appears alsoto be an optimum size of particle with a surfacearea which will release silica in sufficient quantityfor a stufficient length of time.

In animal experiments this was found to beabout o.i micron (Tebbens et al., I945). In thecase of asbestos fibres, it has been shown' that

whereas there is an excess of chrysotile over horn-blende varieties in dusts, ashed lung tissues con-tain only hornblende (Sundius, 1938;. Kuhn,194I). It is concluded that it is the chrysotile insolution which is the fibrosing agent. Gardner(I938) demonstrated by animal experiments thatlonger fibres produced a fibrotic reaction whichdid not occur with shorter fibres and concludedthat asbestosis is, at any rate in part, a mechanic-ally conditioned complex of lung changes. Insupport of this mechanical theory, Johnstone(I948) records the clinical observation that workersat the Thetford Mills, exposed to high concentra-tions of extremely fine asbestos dust, did not sufferfrom asbestosis.

Structurally silica shows continuous three-dimensional arrangements of SiO4 tetrahedra andto these may be related such a surface as to pro-duce the characteristic biological effects. Thosesilicates, therefore, which most nearly resemblequartz in having a three-dimensional network ofsilicon-oxygen tetrahedra are likely, theoretically,to produce similar biological phenomena, T'hese


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pneumoconiosis coal miners · pneumoconiosis in coal miners by j. c. mcvittie, m.b., ch.b., d.p.h....

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